Tube expander



Jan. 11, 1966 c. E. ANDERSON TUBE EXPANDER 2 Sheets-Sheet 1 Filed Dec. 21, 1962 INVENTOR.

Clarence E. Anderson ATTORNEY Jan. 11, 1966 c. E. ANDERSON TUBE EXPANDER 2 Sheets-Sheet 2 Filed Dec. 21, 1962 mm mm mm mmm mom 5 mm 6, 0 0 mm United States Patent 3,228,224 TUBE EXPANDER Clarence E. Anderson, Wadsworth, Ohio, assignor to The Babcock & Wilcox Company, New York, N.Y., a corporation of New Jersey Filed Dec. 21, 1962, Ser. No. 246,482 4 Claims. (Cl. 72123) This invention relates to multiple roll tube expanders, and more particularly to a retractable tube expander for use in expanding relatively light gage tubes such as might be used on a vapor generator air heater or a condenser into tube holes within a tube sheet.

Present day tube expanders usually include a tapered mandrel and three circumferentially arranged rolls which are held in place within a rotatable roller cage or body. At least one of the rolls is set at a slight self-feed angle, i.e., the axis of rotation of the rolls is angled slightly with respect to the longitudinal axis of the tube being expanded. When the tapered mandrel is engaged with the rolls and rotated, rotary movement is imparted to the rolls, the selffeed angle causes the mandrel to travel axially, and the rolls are thus urged radially outward into-engagement with the inner wall of the tube. Thus, the rolls are in a sense screwed into the tube, the radial travel of the rolls per turn of the mandrel in a typical tube expander being about .004 inch. In removing the mandrel from the expander head after completing the expanding operation the rotary drive is reversed, and the mandrel is screwed outwardly at the same rate at which the rolls were advanced until the radial forces have been negated. The entire expanding cycle with this known type of expander requires 35 to 40 seconds. Utilization of the self-feed feature causes the angled roll to engage with the mandrel in essentially point contact, which results in severe wear on the working surfaces of both the mandrel and the rolls. Also, because the rolls are being fed into the tube, the forwardmost portions of the working surfaces of the rolls are required to do the greatest amount of work, again resulting in accelerated wear on the rollers.

Several additional problems have been attendant with the use of presently known tube expanders in applications where a multiplicity of tubes are rolled into a single tube sheet. With the one end of a tube secured while the other is rolled into a tube sheet, a residual stress remains in the tube sheet because of the torsional effect of the rolling on the tube prior to its engagement with the tube sheet. After a large number of tubes are so rolled into a tube sheet, the cumulative residual stress has a tendency to twist the tube sheet out of alignment. Obviously, the extent Or degree of expanding of any one tube is determined by the judgment of the operator. Thus certain tubes may be over-rolled while others may be under-rolled, depending upon the operators skill.

It is an object of the present invention to reduce the amount of time required to expand a tube. An additional object is to provide a tube expander wherein the wear on the mandrel and rolls is minimized by effecting line contact rather than point contact between the mandrel and the rolls during the entire tube expanding operation, with the work of the expansion of the tube being evenly distributed over the working surface of the rolls. Still further objects of the present invention are to alleviate the problem of residual torsional stress in the tube sheet into which the tubes are rolled, and to provide a tube expander which characteristically insures that, with the degree of expansion preset, uniform optimal expansion of a plurality of tubes may be accomplished by an unskilled operator.

In the present invention, the above mentioned objectives may be attained by providing tube expanders with ex- 3,228,224 Patented Jan. 11, 1966 panding heads, each of which is to be inserted into its respective tube end, preparatory to initiating the expanding of the tube. Once in position within the tube end, the expander head remains axially stationary during the entire expanding operation. 'Each head includes a plurality of planetary, radially movable rolls or rollers having frustoconical working surfaces and being held in circumferentially spaced relationship by a rotatable cage. A mandrel with its longitudinal axis substantially co-axial with the longitudinal axis of the tube to be expanded and having an oppositely tapered frusto-conical working surface, is provided for insertion into the expander head. The arrangement of the mandrel and rolls is such that the imaginary apex angle of the mandrel working surface is twice the imaginary apex angle of the working surface of each of the rolls; moreover, the axis of rotation of each roller is in a plane common with the longitudinal axis of the mandrel and is inclined with respect to this axis at an angle equal to half its imaginary apex angle. This relative angular arrangment of mandrel and rolls provides line contact between the rolls and mandrel during the expanding operation and allows the innermost working surfaces of the rolls to be parallel to each other 'during the entire operation so that wear on the rolls is minimized and the work of expansion is uniformly distributed over the entire working surface.

The mandrel (or mandrels, as in a multiple head ex pander) may be attached to a fluid operated piston to selectively urge the mandrel into or out of engagement with the rolls. A motor, connected to the mandrel, is slidably engaged with the piston so that both rotary and axial movements may be imparted to the mandrel simultaneously and independently. A coordinated control system, including an adjustable device for limiting mandrel travel, is also provided for operating the piston and motor.

In another embodiment of the invention, the axial travel and rotary movement of the mandrel may be accomplished by a screw feed mechanism employing an adjustable clutch to limit the axial force exerted by the mandrel during expansion.

In the twin or multiple head embodiment of the tube expander, a gear train may be provided for rotating both mandrels simultaneously from a common motor, or separate motors may be employed for driving each mandrel. Advantageously, the mandrels in a twin head expander may be rotated in opposite directions to nullify the elfect of residual torque stress in the tube sheet into which the tubes are being expanded.

The various features of novelty which characterizes the invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating ad vantages and specific objects attained by its use, reference should be had to the accompanying drawing and descriptive matter in which there is illustrated and described a preferred embodiment of the invention.

Of the drawings:

FIG. 1 is a schematic sectional view of the tube expander head showing the relative relationship between the rolls, the mandrel, and the tube to be expended;

FIG. 2 is a sectional view taken along line 22 of FIG. 1;

FIG. 3 is a sectional view of a single head tube expander having a piston operated mandrel feed;

FIG. 4 is a sectional view of a multiple head tube expander;

FIG. 5 is a schematic control diagram for the tube expanders shown in FIG. 3 and FIG. 4;

FIG. 6 is a sectional view of a tube expander having a screw operated mandrel feed.

In the drawings FIGS. 3, 4, and 6, are shown various tube expanders of the same general type and embodying the inventive concept. The expander heads 11 of each of these expanders are similar, and sectional views of the head are shown in FIGS. 1 and 2. The cage or frame 12, which holds the rolls or rollers 13 circumferentially in place, is not shown in FIGS. 1 and 2, and only a single roll 13 is shown in FIG. 1 so that the relationship between the mandrel 14 and rolls 13 may be more clearly depicted.

In FIGS. 1 and 2, the end of a tube 15, shown extending through a tube hole or bore 16 into a tube sheet 17, is in position to be rolled or expanded within the hole in the tube sheet 17. The tube expander head 11, positioned within the tube end, has three radially movable rolls 13 of circular cross section evenly spaced circumferentially about the center line of the tube, and a cooperating mandrel 14 which extends substantially coaxial with the longitudinal axis of the tube into the central space formed by the rolls 13. The mandrel 14 has an inwardly tapered, frusto-conical working surface 14 which engages with the outwardly tapered working surface 13 of the rolls 13. The imaginary apex angle A, as projected from the working surface of the mandrel 14, is numerically twice the imaginary apex angle B as projected from the working surface of each of the rolls 13. The axis of rotation 19 of each of the rolls 13 is inclined with respect to the longitudinal axis 18 of the mandrel at an angle C which is numerically equal to one-half of the imaginary apex angle B. Additionally, the axis of rotation 19 of each of the rolls 13 is in a plane common with the longitudinal axis of the mandrel 14. It should be noted that with this specific construction, the relationship of the mandrel 14 and rolls 13 is such as to afford line contact between them. This distinctive characteristic minimizes Wear of the working surfaces during prolonged use of the expander. Additionally, it should be noted that during the expanding operation, when the mandrel 14 is axially urged into engagement with the rolls 13 and as a consequence the rolls 13 are moved radially outward, the outermost surfaces of the rolls, i.e., the surfaces which are at the instant in contact with the tube wall, will be in parallel relationship with each other at all times. As a result, the work of expansion will be evenly distributed over the entire length of the roll working surfaces 13 during the entire expanding process, thus minimizing localized wear on the rolls 13.

In FIG. 3 is shown a single head tube expander, employing a piston to axially drive the mandrel. The expander head 11 is shown inserted in the end of a tube 15 which is to be expanded within a tube hole into engagement with a tube sheet 17. The cooperative arrangernent of the rolls 13 and the mandrel 14 is as described above with respect to FIGS. 1 and 2.. The spaced, radially movable rolls 13 are circumferentially fixed relative to each other by the roller cage 12 which is formed with longitudinally slotted openings to receive the rollers 13. A threaded shank portion 12A of the cage 12 extends outwardly from the working portion of the head 11, and at its outermost end receives a lock nut 20 which contacts with the adjacent race of a ball thrust bearing 21. The lock nut 20 may be locked to the shank 12A by means of a set screw, (not shown), threaded into the hole 20A provided in the lock nut 20. The inner race of the hearing 21 engages the shoulder 22A on the thrust collar 22, the innermost end of which engages the tube sheet 17 and thus limits the distance the head 11 may be inserted into the tube 15. From this description it may be seen that, when the head 11 is inserted into the tube 15, its axial position is fixed by virtue of the engagement of the thrust collar 22 with the tube sheet 17. It should be also observed that the head 11 is free to rotate relative to the thrust collar 22 since the bearing 20 is interposed between these two components.

The outermost surface of the thrust collar 22 is threadably engaged with one end of the cylinder extension member 23, the other end of which is also threaded for attachment to the collar 29A, projecting from the cylinder end plate 29. Both ends of the cylinder extension member 23 may be locked by means of set screws (not shown) threaded into holes 23A. The tubular air cylinder 24 is threadably engaged at its forward end with the cylinder end plate 29 and at its rear end with the air cylinder cover 25, which is formed with a central bore 25A through which the air motor drive shaft 26 is received. An air motor 31 is attached to the cover 25 and is arranged and constructed to rotate the shaft 26 in response to a signal from the control system to be hereinafter described. An O-ring 27 is provided in a recessed portion of the cover 25 between the shaft 26 and the bore 25A as a seal to prevent air leakage from the air cylinder 24 through the bore 25A. The shaft 26 is formed with a tapered bore into which is received the shank portion 30A of the drive member 30. A lock nut 28, threadably engaged with the end of the shaft 26, holds the drive member 30 in engagement with the shaft 26. Projecting axially of and into the cylinder 24 is the hexagonal drive portion 30B of the drive member 30.

A double-acting piston 32 is disposed within and arranged to move axially of the cylinder 24, and divides the cylinder space into a forward chamber 40 and a rear chamber 41. Threaded openings 29B and 258 leading respectively to the forward chamber 40 and the rear chamber 41 are provided for the introduction of actuating air into the cylinder chambers. Suitable fittings (not shown) are threaded into the openings 29B and 25B to connect the cylinder chambers 40 and 41 respectively to a control system to be hereinafter described. O-rings 33 are provided on the outer circumference of the piston 32 and cooperate with the inner wall of the cylinder 24 to efiect a seal between chamber 40 and 41. The piston 32 is connected to the axially extending piston rod 34 by roller thrust bearings 35 which allow the piston rod 34 to rotate relative to the piston 32. The bearings 35 engage the flanged portion 34D at their forward end and are held in place at their other end by snap ring 34E. The piston rod 34 is formed with a hexagonal opening 34A in its rearmost portion and into which the hexagonal drive portion 30B of the drive member 30 is slidably received. The forward portion of the piston rod 34 which extends through the bore 29C in the cylinder end plate 29 is formed with a hexagonal opening 34B and annular recess 34C into which is received the corresponding hexagonal shaped drive portion 14A of the mandrel 14. The mandrel drive portion 14A is held in engagement with the piston rod 34 by a lock nut 36 which threadably engages the piston rod 34. An O-ring 37 and a needle bearing 38 are provided between the piston rod 34 and the bore 290 and the collar 29A respectively to prevent air leakage from the forward chamber 40- through the bore 29C and to facilitate rotation of the piston rod 34 relative to the cylinder end plate 29.

From this description, it can be seen that the mandrel 14, With its drive portion 14A in engagement with the opening 34B, can be rotated by the air motor 31 through the shaft 26, drive member 30, and piston rod 34. It should be observed that the mandrel 14 can be moved axially by admitting air into openings 25B or 29B to operate the piston 32 within the cylinder 24 and that this axial movement can be accomplished independently of rotational movement of the mandrel.

The tube expander shown in FIG. 4 is a twin-head, piston operated unit which works on substantially the same principle as the single-head expander shown in FIG. 3. For uniformity of description, parts performing the same function and being of substantially the same structure are given the same reference number designations in both figures.

In FIG. 4, the relative arrangement and functions of the air motor 31, air motor drive shaft 26, piston 32, piston rod 34 and cylinder 24 are similar to that previously described in relation to FIG. 3. Also, the cylinder chamber is divided by the piston 32 into a forward chamber 40 and a rear chamber 41 with appropriate air inlets opening into each chamber. The control lines 48 and 50 respectively lead to the rear and forward chambers 41 and 41) of the cylinder 24 and correspond to the lines having the same reference numbers in FIG. 5 (to be described later). The heads 11 of the tube expander shown in FIG. 4 comprise components similar to those described for the expander of FIG. 3, in that each has a mandrel 14 and rolls 13 having the same cooperating relationship described with respect to FIGS. 1 and 2.

The thrust collars 22 are connected together by and threadably engaged in the end plate 52A of an open sided pedestal 52, which is formed with a pair of longitudinally extending legs 52B and threadably connected at the opposite end 520 of the pedestal 52 with the collar 29A on the cylinder end plate 29. The central portion of the end plate 52A is formed with a post 52D into which is threaded a bleeder valve 51 to be described hereinafter in conjunction with the control system.

The end of the piston rod 34 which extends through the bore 29C is fitted with a centrally positioned shaft 56 and associated driver gear 53 that rotates with the piston rod 34. A pair of driven gears 54 are positioned on opposite sides of and driven by the driver gears 53, the center-to-center distance between the axes of rotation of the driven gears 54 being equal to the center-to-center distance of the tubes to be expanded. A mandrel 14 is attached to each of the driven gears 54. The driver and driven gears 53 and 54 are suitably encased in a housing 55, and all of the gear shafts are provided with the necessary thrust bearings (not shown) to facilitate rotation. An internally threaded sleeve 57 is attached to the forward end of the shaft 56 and an adjustable limit nut 61) is threaded into the end of the sleeve 57, with the limit nut 61 in alignment with the bleeder valve 51 mounted on the pedestal end plate 52A.

From the above description, it will be appreciated that gears 53 and 54, the mandrels 14 and the limit nut 60 move with the piston 32 during the tube expanding operation.

FIG. 5 schematically shows the major components of the tube expanders described in relation to FIGS. 3 and 4 with a control system arranged to operate these piston type expanders. In this diagram, the identification numerals of the expander correspond to like parts shown on the expanders of FIGS. 3 and 4.

The air motor 31 is shown as being slidably engaged with the piston rod 34 through the drive shaft 26. The piston 32 divides the cylinder 24 into forward and rear chambers and 41 respectively. The principal element in the control system is a four-way valve 42. An air supply line 43 supplies air to both the valve 42 through line 44 and to the air motor 31 through line 45. Rotation of air motor 31 may be commenced or terminated by suitably operating valve 46. From the diagram it can be seen that the air motor 31 may be operated independently of the rest of the system, if desired.

For the purposes of description, it will be assumed that the piston 32 is in its fully retracted position as shown in FIG. 5. The operation of the valve 42 is such that by opening bleeder valve 47, air is admitted through line 48 into the rear chamber 41 and pressure is exerted on the piston. The forward chamber 40 is simultaneously relieved of pressure through line 50 through interconnection with the four-way valve 42, thus allowing the piston 32 to move forward and assume the position indicated by piston 32'. When it is desired to return the piston to its original position, valve 51 is opened, thus causing the four-way valve 42 to admit air to chamber 40 through line 50. Meanwhile, the pressure in chamber 41 is relieved through line 48 and the four-way valve 42, and the piston 32 returns to its original position.

To further clarify the operation of this tube expander, a complete tube expanding sequence will be described based on the drawings FIGS. 4 and 5. The expander heads 11 are first inserted into their respective tubes 15. The air motor 31 is then started by opening valve 46, thus causing both mandrels 14 to rotate. Immediately thereafter the bleeder valve 47 may be manually opened causing air to be admitted to chamber 41 of the cylinder 24, and through operation of the piston 32 thereby moving the mandrels 14 axially and into engagement with the rolls 13. By virtue of the rotation of the mandrels 14, the rolls 13 roll against the inner wall of the tubes 15, and axial thrust of the mandrels 14 causes the rolls 13 to move radially outward so that the tubes 15 are expanded into the tube holes in the tube sheet 17 When the mandrels 14 have travelled axially forward the requisite distance to effect the desired degree of expansion of the tubes 15, the bleeder valve 51 is actuated by the preset adjustable limit nut 60. This causes air to be admitted through four-way valve 42 and line 50 into the forward chamber 40, thus exerting pressure on the piston 32 and retracting the mandrels 14 to their original positions. By retracting the mandrels 14 from the heads 11, pressure is relieved from the rolls 13, and the heads 11 may be manually withdrawn from the tubes 15 by simply picking up the entire tube expander. The unit is then ready to again be positioned preparatory to starting another expanding operation.

It will be appreciated that the multiple head tube expander shown in FIG. 4 could be altered without departing from the spirit of the invention. For example, a gear train could be incorporated to impart opposite rotations to the mandrels 14, or separate rotary drives could be used on the mandrels 14. It should be recognized that rotating the mandrels 14 in opposite directions will have the effect of nullifying the cumulative residual torque build-up that is set up in the tube sheet 17 by the rotational forces imposed on each of the tubes 15 during expanding of the tubes into holes in the tube sheet 17.

The tube expander shown in FIG. 6 differs from those previously described in that the axial movement of the mandrel is imparted by a screw mechanism rather than by a piston-cylinder apparatus. However, in this embodiment the components engaging the tube 15 and the tube sheet 17 are also similar to those described for the other embodiments.

In the screw operated expander of FIG. 6, the cylinder extension 23 is threadably engaged with the tubular casing 70 which houses the screw mechanism 71. The outer end of the casing 70 is closed by a threadably engaged end cap 72 having a bore 72A therethrough in which is received the motor drive shaft 73. The drive shaft 73 is driven by a motor 79 which is secured to the end cap. The shaft '73 has a tapered bore into which is received the correspondingly tapered shank portion 80A of the drive member 80. The hexagonal drive end 80B of the drive member 80 extends axially into the screw mechanism 71. A locking nut 74 holds the drive member 80 in engagement with the shaft 73.

The hexagonal drive end or portion 80B engages with a mating inner surface 81A at the outer end of the drive screw 81, so that the drive screw 81 rotates with the end 80B of the drive member 30 and is free to axially slide with respect thereto. The forward end of the drive screw 81 is formed with a hexagonal recess 81B which receives the hexagonal drive portion 14A of the mandrel 14. The mandrel portion 14A is held in engagement with the drive screw 81 by locking nut 93. It should be observed from the above that the mandrel 14 and drive screw 81 will rotate when the shaft 73 is rotated, and that axial travel of the drive screw 81 and mandrel 14, with respect to the drive member 80, is also achieved.

The outer surface of the drive screw 81 is formed with heavy duty square threads which engage threads of similar contour formed on the forward inner portion of the screw sleeve 84. Threadably connected to the outer end of the screw sleeve 84 is an outwardly extending annular lock ring 85, both the flat surfaces of which engage the races of the two spaced thrust bearings 86. The lock ring 85 is fixed relative to the screw sleeve 84 by set screw 87. The bearings 86 are held in place by a tubular drive housing 88, which is concentric with and positioned outside of and around the screw sleeve 84, and threadably connects with the end cap 72. The screw sleeve 84 is free to rotate in the forwardly extending portion 88A of the housing 88 which surrounds it. The forwardmost end of the screw sleeve 84 is formed with an outwardly extending flange 84A which is attached to the lower clutch plate 90. The upper clutch plate 91 is attached on its inner surface to the portion 88A of the housing 88 by a key 92 which allows the upper clutch plate 91 to slide axially with respect to the housing 88 but restricts relative rotation therebetween. A clutch coil spring 93 is engaged at its forward end with the upper clutch plate 91 and at its rearward end with a spacer ring 94 which is held against the stepped portion 88B of the housing 88 by pressure of the spring 93.

The working surfaces of the clutch plates 90 and 91 are each formed with a series of mating, shallow teeth having tapered edges, so that they will disengage and rotate relative to each other when the torque which is generated during the tube expanding operation reaches a predetermined value where it overcomes the force holding the plates together. It should be recognized that this clutch construction is such that the relative rotation of the clutch plates will not damage the mating teeth. Obviously, other known types of clutch arrangements might be used in place of the one here described.

From this description it can be seen that the screw sleeve 84 is free to rotate within the housing 88 and is restrained from rotation only by virtue of the engagement of the clutch plates 90 and 91 which is maintained by the force exerted on the upper clutch plate 91 by the compressed spring 93. It will be observed that the force holding the clutch plates 90 and 91 together could be altered by inserting a spacer ring 94 having a different thickness than the one shown, or by changing the spring to one of heavier or lighter gage material.

Threadably engaged with the external surface of the upper clutch plate 91 is a forwardly extending tubular clutch housing 95. A bearing retainer cap 96 is threadably engaged with the forwardmost end of the clutch housing 95 and holds the thrust bearing 97 in place. One race of the bearing 97 is engaged with an inwardly extending circular rim 95A of the clutch housing 95, and the other race engages with a small ledge 81C on the outer surface of the drive screw 81 when it is in its retracted position as shown.

To further define the relationship between and to describe the function of the various parts of the tube expander, shown in FIG. 6, a complete tube expanding operation will be followed. The expander is shown in its retracted position, and should be observed that, when it is in this position, the compressed spring 93 exerts a force on the upper clutch plate 91, thereby exerting a force which holds the clutch plates 90 and 91 together.

After the expander head 11 is inserted into the end of the tube 15 with the thrust collar 22 resting on the tube sheet 17, the operator begins the expanding operation by initiating rotation of the motor 79. This causes the drive member 81), the drive screw 81, and the mandrel 14 to rotate. The screw sleeve 84 does not rotate because of its connection to the lower clutch plate 90. Thus the mandrel 14 is moved axially forward by virtue of the threaded engagement between the rotating drive screw 81 and the stationary screw sleeve 84. As the mandrel '14 moves forward, it engages the rollers 13 and urges them radially outward against the inner wall of the tube 15.

Each rotation of the motor 81 moves the mandrel 14 forward a distance equal to the distance between threads on the drive screw 81 with a single pitch drive screw thread, and with each successive rotation, the work done in expanding the tube increases and a greater torque and axial force are set up in the mandrel. When this torque which is transmitted through the drive screw 81 to the screw sleeve 84, reaches a predetermined level, the tendency of the screw sleeve 84 to rotate overcomes the spring force holding the clutch plates and 91 together and the lower clutch plate 90 rotates. The relative rotation of the clutch plates 98 and 91 will produce a chatter which will serve as a signal to the operator that the expansion has been completed to the desired preset level.

It should be recognized that the extent of expansion would be greater if there were more force holding the clutch plates 90 and 91-together. Thus, by using a thicker spacer ring 94 or a heavier spring 93, the initial force exerted by the spring 93 would be greater, and more torque would be required to rotate the screw sleeve 84 to overcome the force holding the clutch plates 90 and 91 together.

To retract the expander, the operator simply reverses the rotation of the motor 31. Since there is practically no resistance to rotation in this direction, the force exerted by the spring '93 can now easily overcome the nominal amount of torque on the screw sleeve 84. The screw sleeve 84 therefore stops rotating and the drive screw 81 threads its way back to its original position.

This tube expander also has a built-in feature to prevent jamming of the parts should the operator fail to stop the motor 81 when the drive screw 81 is being retracted. In this event, the ledge 81C on the drive screw 81 will engage with the bearing 97 and exert a rearward force on the clutch housing 95. Since the clutch housing 95 is threadably attached to the upper clutch plate 91, it will be forced rearwardly against the pressure exerted by the spring 93 and out of engagement with the lower clutch plate 90. This will again allow the drive screw 81 and screw sleeve 84 to harmlessly rotate together.

Of particular significance is the fact that the screw type expander shown in FIG. 6, when used even by a comparatively unskilled operator, produces a greater uniformity in the degree of tube expanding than has heretofore been possible with known tube expanders. Since the expansion process is automatically terminated upon attaining a given torque or force level in the screw mechanism, it can be recognized that the amount of energy exerted in rolling each tube will be the same. This will produce uniformity in the degree of rolling to which a multiplicity of tubes is subjected, notwithstanding the usual commercial manufacturing tolerances in the tubes and tube sheets.

It has been established that the time required for expanding tubes using the above-described single head expanders of FIGS. 3 and 6 is about 5 to 7 seconds per tube, or less than 20 percent of the 35 to 40 seconds required for tube expanding using presently known equipment. Of course, the total time may be proportionately reduced by using a multiple head expander of the type shown in FIG. 4. The piston type expander has been found to 'be particularly applicable to the rolling of relatively light gage tubes and it has the advantage of being slightly faster than the screw type expander for these applications. However, the screw expander, with its constant, more positive drive mechanism has been found to be preferable for the rolling of heavier gage tubes.

While in accordance with the provisions of the statutes there is illustrated and described herein a specific embodiment of the invention, those skilled in the art will understand that changes may be made in the form of the invention covered by the claims, and that certain features may sometimes be used to advantage without a corresponding use of the other features.

What is claimed is:

1. A tube expander comprising a set of planetary, radially movable rollers having their outermost surfaces in parallel relationship, each of said rollers having a frusto-conical working surface, means for inserting said set of rollers into a tube to be expanded, means restraining axial movement of said rollers with respect to said tube after said rollers have been inserted into said tube, a mandrel having a frusto-conical working surface, fluid operated piston means including a piston and a piston rod connected to said mandrel for axially urging said mandrel so that the working surface of said mandrel engages with the working surfaces of said rollers in line contact to urge said rollers radially outward into engagement with the inner wall of said tube while maintaining said parallel relationship, and means for simultaneously rotating said mandrel, said last named means including a drive motor connected to rotate a drive member which is axially slidably received in an opening formed in said piston rod, said piston rod being connected to said piston through bearing means permitting relative rtation between said piston and said piston rod.

2. A tube expander comprising a head insertable in the end of the tube to be expanded, said head including an axially movable mandrel having a tapered surface, and a set of planetary, radially movable rollers arranged to be engaged with said mandrel in line contact and having their outermost surfaces in parallel relationship during the entire expanding operation, each of said rollers having an imaginary apex angle equal to half the imaginary apex angle of said mandrel and each of said rollers having its axis of rotation in a plane common with the lon gitudin-al axis of said mandrel and inclined with respect to said longitudinal axis at an angle equal to half its imaginary apex angle, means for rotating said mandrel including a drive motor, and means for simultaneously axially urging said tapered surface of the mandrel into engage ment with said rollers, said last named means comprising a cylinder attached to said head, a fluid operated piston slidable within said cylinder, and a piston rod connecting said piston and said mandrel and being axially slidably engaged with said drive motor, said piston rod being connected to said piston through bearing means per mitting relative rotation therebetween.

3. A tube expander comprising a set of planetary, radially movable rollers having their outermost surfaces in parallel relationship, each of said rollers having a frusto-conical working surface, means for inserting said set of rollers into a tube to be expanded, means restraining axial movement of said rollers with respect to said tube after said rollers have been inserted into said tube, a mandrel having a frusto-conical working surface, each of said rollers having an imaginary apex angle equal to half the imaginary apex angle of said mandrel and each of said rollers having its axis of rotation in a plane common with the longitudinal axis of said mandrel and inclined with respect to said longitudinal axis at an angle equal to half its imaginary apex angle, and a positive drive mechanism for rotating and axially urging said mandrel so that the working surface of said mandrel engages with the working surfaces of said rollers in line contact to urge said rollers radially outward into engagement with the inner wall of said tube while main taining said parallel relationship, said drive mechanism comprising a drive motor arranged to rotate a threaded axially movable drive screw connected to said mandrel and constantly threadably engaged with a stationary screw sleeve, and clutch means interconnecting said drive screw and said screw sleeve for limiting the torque transmitted through said mandrel.

4. A tube expander comprising a set of planetary, radially movable rollers having their outermost surfaces in parallel relationship, each of said rollers having a frusto-conical working surface, means for inserting said set of rollers into a tube to be expanded, means restraining axial movement of said rollers with respect to said tube after said rollers have been inserted into said tube, a mandrel having a frusto-conical working surface, each of said rollers having an imaginary apex angle equal to half the imaginary apex angle of said mandrel and each of said rollers having its axis of rotation in a plane common with the longitudinal axis of said mandrel and inclined with respect to said longitudinal axis at an angle equal to half its imaginary apex angle, a positive drive mechanism for rotating and axially urging said mandrel so that the working surface of said mandrel engages with the working surfaces of said rollers in line cont-act to urge said rollers radially outward into engagement with the inner wall -of said tube While maintaining said parallel relationship, said drive mechanism including a drive motor connected to rotate a drive member, a threaded axially movable drive screw connected to said mandrel and formed with an opening into which said drive member is axially slidably received, a stationary screw sleeve constantly threadably engaged with said drive screw, and clutch means interconnecting said drive screw and said screw sleeve for limiting the torque transmitted through said mandrel.

References Cited by the Examiner UNITED STATES PATENTS 612,838 10/1898 Fuhrmann e-t al. 153-82 1,752,408 4/1930 Zein 153-82 2,471,614 5/1949 Gilman 153-82 2,633,165 3/1953 P-alkowski 144-110 2,690,205 9/1954 Stary 153-82 2,772,716 12/1956 Stary 153-82 3,052,972 9/1962 Steinmeyer 29-2405 CHARLES W. LANHAM, Primary Examiner.

WILLIAM J. STEPHENSON, Examiner. 

1. A TUBE EXPANDER COMPRISING A SET OF PLANETARY, RADIALLY MOVABLE ROLLERS HAVING THEIR OUTERMOST SURFACES IN PARALLEL RELATIONSHIP, EACH OF SAID ROLLERS HAVING A FRUSTO-CONICAL WORKING SURFACE, MEANS FOR INSERTING SAID SET OF ROLLERS INTO A TUBE TO BE EXPANDED, MEANS RESTRAINING AXIAL MOVEMENT OF SAID ROLLERS WITH RESPECT TO SAID TUBE AFTER SAID ROLLERS HAVE BEEN INSERTED INTO SAID TUBE, A MANDREL HAVING A FRUSTO-CONICAL WORKING SURFACE, FLUID OPERATED PISTON MEANS INCLUDING A PISTON AND A PISTON ROD CONNECTED TO SAID MANDREL FOR AXIALLY URGING SAID MANDREL TO THAT THE WORKING SURFACE OF SAID MANDREL ENGAGES WITH THE WORKING SURFACES OF SAID ROLLERS IN LINE CONTACT TO URGE SAID ROLLERS RADIALLY OUTWARD INTO ENGAGEMENT WITH THE INNER WALL OF SAID TUBE WHILE MAINTAINING SAID PARALLEL RELATIONSHIP, AND MEANS FOR SIMULTANEOUSLY ROTATING SAID MANDREL, SAID LAST NAMED MEANS INCLUDING A DRIVE MOTOR CONNECTED TO ROTATE A DRIVE MEMBER WHICH IS AXIALLY SLIDABLY RECEIVED IN AN OPENING FORMED IN SAID PISTON ROD, SAID PISTON ROD BEING CONNECTED TO SAID PISTON THROUGH BEARING MEANS PERMITTING RELATIVE ROTATION BETWEEN SAID PISTON AND SAID PISTON ROD. 